Mitt Romney has taken the lead in USA Today/Gallup’s presidential poll for the first time since last September, winning 50% of support compared to 46% for President Barack Obama, according to Market Watch.

It’s also the first time Romney has led in a national poll since mid-January, according to Realclearpolitics.

Only problem for Romney is that he trails Rick Santorum, the former Pennsylvania senator, among Republican voters nationally. Gallup’s most recent GOP poll shows Santorum with a 35% to 27% advantage heading into the critical Arizona and Michigan primaries next week.

Santorum trails Obama, 49% to 48%, in the latest Gallup presidential poll. He’s closed the gap considerably from January, however, when he trailed 51% to 43%.

The Romney-Obama and Santorum-Obama matchups are within the poll’s margin of error, meaning the candidates are effectively tied.

In the last USA Today/Gallup poll in January, Romney and Obama were tied. The December poll showed Obama with a 2-point lead. See Realclearpolitics polling data. The Gallup surveyed polled registered voters from Feb. 16 to Feb. 19.